Now you have me confused. All the installation photos are of a 14-30R, which is a 4-wire circuit requiring a double-pole breaker. The last photo, of a retail box, shows a TT-30R, which is a 3-wire outlet.
Are you going to replace the 14-30R with the TT-30R? I thought you were just going to use an adapter from the 14-30 to a TT-30?
If you are going to replace the 14-30 with the TT-30, ideally you would change to a single-pole, 30-amp breaker. The second (red) hot wire would be removed. However, it is not unsafe to continue to use the double-pole breaker in place now. Just leave the second pole unconnected.